Posts Tagged ‘rainwater’

The Airport is located quite far from the city, about 30 kilometres away. It is too far away from city lines and has to depend on groundwater. It needs 9 million litres per day eventually though for now 5 million litres per day will do. To boot it is located in what was called a ‘dark zone’ by the Central Ground Water Board, meaning groundwater was being exploited beyond recharge potential. An Airport needs water and plenty of it. So what did it do?

For one it requested and sourced fresh water from the city paying Rs 66 a kilo-litre, a high price which gave the water utility supplying it some monies. This fresh water is limited to about 1.5 million litres daily. It then did a smarter thing, it bought tertiary treated waste-water and a full 2 million litres of it daily and it paid Rs 25 a kilo-litre for this treated waste-water. This was separately stored and used for the vast beautiful landscape springing around, a huge bio-diversity of plants and even a small wetland.

For the internal waste-water generated it set up its own sewage treatment plant using extended aeration system. This treated water is then reused for flushing the toilets in the airport premises as well as for the air cooling systems. The sludge generated from the sewage treatment plant is composted and reused as manure for the landscaped area.

An internal waste-water treatment plants treats all waste-water as well as waste from aeroplanes

Runways and the area surrounding it generate large quantities of storm water when it rains. It is therefore very important that this run-off be collected and quickly disposed off and flooding avoided. With more than 310 recharge wells located in the storm water drain or immediately adjacent to it a large volume of the rain is recharged into the aquifer. Well designed storm-water drains then take away the rest of the rainwater to an adjacent lake which is capable of receiving this large flow of rain.

Two things have happened due to these good efforts. Four large open wells which were old existing constructions have been rehabilitated, cleaned up and repaired. Pumps and a filter have been attached and the water quality tested. It is found that this is very high quality, sweet potable water. Thanks to the recharge efforts the wells stay full even during summer. Up-to 800,000 litres of water can be drawn from these open wells daily and in an emergency they can replace the mains water from the city. A landscape which was once a dark zone, given a holiday for high extraction from bore-wells and with enough recharging can be revived to such an extent that open wells can have water.

Recharge of rainwater has helped aquifers rejuvenate with fresh clean water

From the airport buildings rainwater is stored in large underground sump tanks of about 1.5 million litres capacity and reused after treating. Excess water from the sump tanks is then allowed to flow into storm drains and recharge the aquifer as well as flow into the adjacent lake.

The revival of the adjacent lake also means that villages and towns adjacent to the airport, such as the town of Devanahalli, can now think of sourcing groundwater from adjacent to the lake to fulfill the towns water requirements.

Sludge drying beds

Economic activity and service activity like airports are essential for economic growth and to spur the progress of a city. Instead of seeing it as placing demand on water services through innovative design they can absorb waste-water from cities and be able to use it to meet its requirements. Through waste-water treatment and reuse and through rainwater harvesting groundwater aquifers can be revived and lakes kept full. These can then be of great help to surrounding communities. The Kempegowda International Airport at Bangalore showcases just that. This is water wisdom.

It is a strange place to have placed four towers and have started a city but perhaps Magadi Kempegowda was not thinking of water when he had his grand dream. The city now has outgrown those four towers and the one small stream which was the only part of a running water landscape is now desecrated beyond measure and called the Vishabhavati (the poison river) from the original Vrishbhavati (that which originates from the mouth of a bull) .

As early as the 1850’s the British were complaining about the water and sanitation systems. It also did not help matters that sewage was being left into the very source from where water was being drawn. Both Ulsoor and Dharmambudhi Lake being the source and the sink.

In a pioneering effort of its kind, most probably aided by the fact that this was city not near a perennial water source and there was always a sense of shortage, the city started to search for water from far. Hessarghatta on the Arkavathy reservoir 24 km away was first developed as a storage dam. Steam engines were used to pump water into the city and when electricity came that then replaced the steam engines. In each case Bangalore was a pioneer in the use of steam and electricity to pump water to itself. Hessarghatta was found short to slake the cities thirst and Thippagondanahally on the junction of the Kumudvathi and Arkavathy came into being as a new reservoir in addition to the Arkavathy in the mid 30’s. The city continued to grow and in the 1970’s the Cauvery was tapped at Torekadinahalli, pumped to a distance of 95 kilometres and 300 metres high to quench the city’s thirst. This was a remarkable engineering feat by a remarkable institution the Bangalore Water Supply and Sewerage Board- BWSSB – the first exclusive city level water and sanitation utility created in India. Stages 1, 2, 3 and 4 and phases 1 and 2 of stage 4 have kicked in and one of the costliest water in Asia comes after being pumped in three stages into the city. Alas the limit to drawal also has been reached and there is no more water for the city unless there is a redrawing of the water requirement between the irrigation and the urban sector in the Cauvery basin part of Karnataka.

In the meantime the city found out an uncomfortable truth, not all of it was in the Cauvery basin. In fact 2/3rds of it was outside the basin and in a river called the Dakshina Pinakini or the Ponnaiyar so that part was not entitled to water from the Cauvery basin or so said the tribunal.

In true government style a committee was formed to find out how the growing needs of the economic and domestic demand of the city could be met. Proposals include getting water from the Hemavathi, the Sharavathy as well as the west flowing rivers. These of course are huge projects involving lots of money and energy, something which should get the construction lobby salivating.

In the meantime there are practical proposals such as rooftop rainwater harvesting, the rejuvenation of the remaining lakes of the city, the recharging and the management of the groundwater in the city and most importantly the treatment and reuse of waste-water which show tremendous opportunities.

While the city gets 1400 million litres of piped water supply, the equivalent of 3000 million litres per day falls as rain on it. The total volume of wastewater available for reuse is 1100 million litres and the amount of groundwater that can be drawn sustainably is close to 600 million litres per day provided it is adequately recharged.

Do the math then

Average demand 200 Litres per capita per day

Total; available water

From Cauvery 1400 million litres per day

From groundwater 600 million litres per day

From recycled waste-water 1100 million litres per day

From rainwater 600 million litres per day ( 20 % rain harvested)

Total 3700 million litres per day

Good enough for a population of 18.50 million

…and if we get demand efficiency right and demand down to 100 litres per dapita per day

37 million people of Bangalore can be served ( current population 9 million)

Unfortunately the institution in charge of water supply is not completely geared to undertake a water management approach. It has no skill set for example in lake management or in hydro-geology.

If institutional capacities are built up, if there is a strong vision and an accountable authority created Bangalore in its pioneering way can overcome its water shortage problems. Else it will be forever condemned to become dependent on a tanker economy. The choice is ours and the time is now.

At first glance you see a protective fence which is not impressive but as you approach the magnificence of the structure strikes you , a beautiful 120 feet diameter open well full of water and you wonder whether this is the Bangalore where groundwater is supposed to have sunk to 1250 feet. This residential layout on the South of the city has done a magnificent job of managing its water purely through community action. A dynamic association has taken charge and the committed team first cleaned up the ‘Rajakaluve’- the main stream linking water above and beyond , passing through the layout. Its attention was then focused on the beautiful heritage well on campus. The well was cleaned and a 100 truck loads of silt removed. The silt was place in the gardens and the open spaces rich in fertile soil.

A beautiful old well revived and recharged – full of water

The well now becomes a supplemental source of water for non-potable use and in case of an emergency with treatment for all uses. Each house in the layout has been encouraged to go in for rainwater harvesting. In the storm drains which run around, all of them are maintained clean and percolation wells are being placed so that the road run-off is recharged into the ground. Ultimately all run-off will be sent into the aquifer with the site becoming a zero discharge area for storm-water.

A waste water treatment plant hums daily, treating and cleaning 200,000 litres of sewage from the entire colony. This treated waste-water too is reused in the layout. A 100 trees are planted every year and the waste water is used to feed the trees and the parks.

The community building where the residents meet , collects every drop of rainwater falling on the roof in large rain barrels and reuses them.

Rainwater Barrels collect rooftop rain

On the day one visited the campus children had gathered at a science fair and were demonstrating various experiments that they had set up. Most of them centred around water. A group of them had already been taken for a tour of the layout explaining what was happening with water and the necessity to keep the roads and storm water drains clean as well as to take care of the trees for the birds that are around.

A turtle was spotted in the well and was swimming about merrily, a cause for some excitement.

When communities come together it is possible to achieve the unthinkable, that is a clean environment and plenty of water with a bit of heritage thrown in. The more we expand thisn space the better for our urban areas. In this community awareness and action lies water wisdom.

Summary: It is in years of plenty that we should stock up for times of shortage

Many people are moving into a problem solving mode but it needs institutional reinforcement to help achieve maximum benefits.

The major Public Sector undertaking has a very large campus and has a huge water demand. It draws water from the Bangalore Water Supply and Sewerage Board and pays a hefty Rs 60 per kilo-litre for the water. Being water smart, it has set-up a waste-water recycling unit and ensures that all waste-water is treated and reused for non-potable purpose particularly gardening .Lawns are extensive in the campus and is needed for dust suppression. The unit has also set up a huge lake to harvest run-off from its vast land. More than 170 million litres of storm-runoff is stored in this vast lake.

Their attention has turned to the large rooftop areas they have on campus. From 11,500 square metre of roof area, they simply connected the rainwater downpipes and brought it into a small 20,000 litre sump tank. From here they have put a pump to send the water directly into a much larger sump tank which takes water through a Reverse Osmosis unit. This R.O. water is needed for their manufacturing purpose. The investment they had to make was Rs 10 lakhs. Was the investment worth it?

The benefits translate as follows. They are likely to harvest 10 million litres of water annually. This will result in a savings of Rs 6 lakhs annually. The payback period for the investment is thus less than 2 years. There are other benefits. The embodied energy in alternate water, either from the BWSSB or bore-wells, is roughly 2 units of power per kilo-litre of water. The industry will therefore save nearly 20,000 units of power annually. This also translates as a savings in carbon emissions.

There are other benefits. The harvested rainwater is very soft with a Total Dissolved Solids of less than 50 ppm. This is likely to reduce further as the initial leaching of cement from the sump tank and the pipes become less. As against this the water they used from bore-wells had a TDS level of nearly 1000 ppm. The life of the membrane used for R.O. now increases. The reject water from the R.O. has fewer salts and can be recycled more easily than before.

The advantage is clear and it is likely that the industry will move quickly ahead to cover all roof-tops with rainwater harvesting systems. This means that over 100,000 square metres can be covered and over 100 million litres of rainwater harvested. No small feat for an industry located in a water scarce city.

A University: The University of Agriculture with a sprawling 1200 acres campus was once outside the city. Now it has become integral and falls within the Corporation Limits. Its water demand for agricultural crops is high. Most of the water comes from bore-wells. These are over exploited and many have gone dry. It has designed for itself a watershed based rainwater harvesting system. Thanks to a bountiful September rain a great amount of water has been collected and allowed to percolate into the ground. Many bore-wells have revived and are humming with water. The University is able to meet its water demands and students and Professors can continue to develop knowledge with experiments on the ground.

Groundwater banks are being created in the city by institutions that occupy large tracts of lands and have large rooftops. These efforts supplement the water delivery to the city and make the city water smart. Things have to be scaled up and more such institutions brought into the rainwater harvesting community. Further deeper understanding of how much water is actually recharged into the ground, what is a reasonable water demand to keep the groundwater banks humming for 2 to 3 years will ensure that the water shortfall in the city is overcome. Creative solutions using knowledge is the hall mark of the city and in this lies water wisdom.

The monsoon is a magical time in India. The season of the wind, clouds and rain brings joy to a parched land. Rainwater to India is a gift from the Indian Ocean. The clouds do the couriers job and the winds play assistant. When i falls on our heads it is good to keep a clean catchment and then collect it in Rain barrels. You can then put this soft water which is slightly acidic to good use . Apart from drinking the water (after checking for purity) you can make coffee from it.

A clean roof , a good cloth filter and a food grade HDPE tank to store rainwater

Clean soft water slightly acidic and with a high Dissolved Oxygen content – rain

As the city expands and buildings fill it up to find open space becomes difficult. In Bangalore in the small sites it is impossible to have even a small garden. About 60 to 70 % of inner Bangalore will be roofs as a look at Google earth will show.

For an urban planner like me and for Chitra an Architect this was a fascinating finding. What do roofs do and how are they designed? Unfortunately we seem to poorly design our roofs apart from ensuring that they keep out the sun, rain and the elements. Most of the concrete and steel in the roof goes towards carrying its own self weight. Architect Laurie Baker had shown that we could make roofs lighter by using a filler slab. Waste tiles were what he used as a filler material. This made roofs lighter, require less concrete and steel and also look beautiful from the inside. Scientists such as Prof Jagadish and Dr Yogananda had designed the flat tile arch panel roof, which was precast and which also was structurally lighter, more efficient and had a different aesthetic quality. We therefore used these roofs in our house.

A filler slab roof using Mangalore Tiles as a filler material

A calculation on what was happening the outside of the roof was also interesting. Almost all the rain on the building site falls on the roof. In Bangalore it can rain 970 mm in an average year. This meant that our house roof with an area of 100 square metres had 97,000 litres of pure rainwater falling on it. With the idea why allow it to go waste, we started to harvest it? This harvesting was done at many levels.

From the staircase rooftop which had an area of 10 square metres, we placed a Rain barrel and collected the water on the roof itself. A small platform was designed and the 500 litre Rain Barrel placed on it. On the staircase roof we placed a gutter to collect the rain. This came down into a vertical pipe with an end cap called the first rain separator. During the first rain and subsequently when we want to clean the roof or the rain gutter we open the cap and the dusty water flows out through the first rain separator. Then after a ‘Y trap’ rainwater flows in through a ‘dhoti filter’ into our rain barrel. We checked the rainwater quality using a H2S strip test and found the water potable. Sometimes when there is slight contamination we use a method called SODIS (Solar Disinfection) to treat the collected rainwater for drinking purpose. Here you fill a PET bottle with the rainwater and leave it in the sun for 5 hours. The water is now sterilized and can be brought into the house cooled and is ready for drinking. This is not a low cost solution for water treatment but a no-cost solution. Our annual requirement of drinking cooking water comes from this rain barrel alone.

We also have an Ecosan toilet on the terrace. This pan in the toilet separates solids and liquids at source. We collect the urine in a barrel, dilute it and use it as a fertilizer for our terrace garden. The solids are covered with ash every time we use it. This is then transferred to some Blue drums we have kept on the terrace and again covered with earth or straw. We then plant trees in these drums. Trees such as Papaya, lemon, curry leaves, sapota are planted and they grow well. No waste from our toilet on the terrace leaves the roof.

The rainwater falling on the Ecosan toilet too is collected in a 200 litre rain barrel and used for ablution purpose.

We have a box type solar cooker to cook our lunch on the terrace. A solar water heater heats water for bath and for the kitchen. During cloudy days we use a ‘Gujarat boiler’ which uses bio-mass for the water heating. The Gujarat Boiler also generates ash for us to use in the Eco-san toilet. We have planted many trees in front of the house and the twigs and branches from the trees are used for the Gujarat Boiler.

Next we have placed a bathroom on the terrace itself. This also has a front loading washing machine which is one of the most water efficient ones in the market. We collect the water from the bath we have on the terrace bathroom as well as from the washing machine in a small ferro-cement tank placed just below the roof slab. We then pump it up to a planted reed filter to clean up the grey-water using a small pump. The reed filter is Cattails – reeds found in lakes- placed in 4 blue drums. In a fifth drum we have sand and gravel filter to clean up the grey-water further. This treated grey-water is then used for the terrace garden where we sometimes grow rice paddy. Some extra grey-water is also used for flushing the toilet in the ground floor. No greywater is allowed to go waste.

The rice on the rooftop grows well on even a small area. We place 2 sheets of a pond lining material called Silpaulin with a brick edging. The sheet is then filled with a mix of compost, vermi-compost and red earth up-to a depth of 2 to 3 inches. Rice paddy is then planted in it. The water required for the paddy comes from grey-water alone. For the fertilizer the urine from the Eco-san toilet is used. Kitchen waste which is composted is also added to the soil. We have had productions of paddy to the tune of 1 kg per square meter. We have also found that we can grow 4 crops of rice in a year. Millets can also be grown instead of rice. Vegetables such as tomatoes, brinjals, lady-fingers, chilies all grow on the terrace though the monkeys who frequent this place can also be a nuisance at times.

A small wetland has also been created in a ferro-cement tank where different plants and fishes occupy and clean water.

Solar photo-voltaic panels on the roof provide enough power for us to store in batteries and use to light 11 bulbs in the house. The house incidentally has no fans let alone AC’s thanks to the cool terrace as well as thanks to the trees planted on the sides which enfold it in shade.

A well designed rooftop can provide all the water required for a house-hold, provide energy for cooking , lighting and water heating, provide food-grains and vegetables , enhance bio-diversity as well as absorb all the waste-stream from the house from the kitchen and bathroom / toilets and convert it to reuse .

Many parts of the city of Bangalore have lateritic soil and highly weathered rock. By designing storm=water drains correctly and placing recharge wells such as this one, rainwater can be allowed to infiltrate and recharge the aquifer. This recharge well built in June 2004 will be completing 9 years shortly. On an average it has been sending in 1 million litres of rainwater into the ground each year. More such appropriately designed recharge wells will help improve groundwater levels , of course when balanced with managed and controlled withdrawal.